my specs are:6gb ram ddr3nvidia 315m gpu 512 mb 1tb hardriveintel core i3 2.20 ghz turbo boost to 2.90please tell me

I'd go for FS9. It's kind of like if you have to ask, then you know what the response will be. Is this a laptop computer? The graphics "nvidia 315m" generally denotes a mobile setup.If you find that it runs FS9 really well you could then try FSX. But that's a better route than trying FSX and seeing it didn't work well enough and knowing you wasted the money on it. Going with FS9 first still gives you an enjoyable experience, so that it's cost doesn't get wasted.